The purchase of a new high-resolution instrument is proposed. The microscope will be placed under the administration of a central EM facility, which presently supervises the usage of a medium-resolution instructional instrument. The instrument will be made available to all members of the research community, with NIH-supported users having priority. A major users' group of four scientists have prepared this application, whose reseach interests include the structural analysis of energy-transducing membranes, analysis of nervous system structure and synapse organization, the cellular effects of environmental pathogenic materials, and the analysis of nervous system organization in model invertebrates. A much larger group of users will be affected by this upgrading of instrumentation, and their applications have been identified. A plan for the supervision of the instrument has been prepared and a substantial guarantee of financial support from the applicant institution has been secured.